1. Field of the Invention
The present invention is related to a network technique capable of preventing erroneous connections during line setting operation in a network constituted by including a transfer apparatus having a cross connect function.
2. Description of the Related Art
In major networks connected via highspeed optical transmission paths, SONET (Synchronous Optical NETwork) is known in which a synchronized signal group (STSxe2x88x92n: Synchronous Transfer Signal/n=Multiplexing Layer) is directly multiplexed without applying a frame synchronization signal of a high order group.
Since the SONET is the synchronized highspeed transfer system, a network with a ring structure can be readily established. In general, LANs (Local Area Networks) employed in small-scale offices are also arranged by ring-shaped transfer paths. This SONET differs from LANs in that point that, as previously explained, a multiplexed highspeed synchronization signal is transmitted with a predetermined format structure (STSxe2x88x92n).
In the SONET, a basic signal frame STSxe2x88x921 is constituted by an overhead (will be simply referred to as xe2x80x9cheaderxe2x80x9d hereinafter) corresponding to a control signal region, and a payload corresponding to an information storage region.
In a SONET, a node (repeater network element (NE)) is provided within a ring network, and a cross connect apparatus is provided with this node, through which a transfer signal received via a transmission path is added(Add), dropped(Drop), and passes(Pass through).
A difference between this cross connect apparatus and a switching unit (switchboard) is given as follows. The switching unit switches/connects data with respect to each call, whereas the cross connect apparatus determines a transfer path of data in a semi-fixed manner without being closed in response to external setting.
In FIG. 1, there is shown an arrangement of a ring network constituted by a NE xe2x80x9cAxe2x80x9d, a NE xe2x80x9cBxe2x80x9d, a NE xe2x80x9cCxe2x80x9d, and a NE xe2x80x9cDxe2x80x9d.
A cross connect setting operation is performed when the network is established, the line is newly added, or the line is changed. In this case, a network manager executes the cross connect setting operation with respect to a transfer apparatus such as a network management system NMS (Network Management System) from a monitoring/controlling apparatus for this transfer apparatus.
A description will now be made of an example of a cross connect setting operation in a ring network indicated in FIG. 19.
In this drawing, in such a case that a path is constituted by which information of a switching unit xe2x80x9cAxe2x80x9d (2001a) is transmitted via transfer apparatus A, B, C (2002a, 2002b, 2002c) to another switching unit xe2x80x9cZxe2x80x9d (2001z), a signal frame of STSxe2x88x921 (will be handled as xe2x80x9cchannelxe2x80x9d and thus be expressed as an xe2x80x9cx channel (xCH)xe2x80x9d hereinafter) is firstly pass-set from a path HG2 to another path HG1 in the transfer apparatus B (2002b).
Next, the xCH is pass-set from the path HG2 to the path HG1 in the transfer apparatus C (2002c). Subsequently, a DROP setting operation is performed by which the xCH on the side of the path HG2 received in the transfer apparatus D (2002d) is transmitted to the switching unit Z (2001z). As described above, the cross connect setting operations must be sequentially carried out with respect to four sets of these transfer apparatus A, B, C, and D.
Also, with respect to the TSA function, since only the pass-setting operation of the same channel can be executed, the xCH must be unused in not only the transfer apparatus A/D, but also the transfer apparatus B/C. In other words, when each of the above-described transfer apparatus A to D is set, the cross connect setting condition of each of the four transfer apparatus A to D must be confirmed.
As represented in FIG. 19, when data is transferred from the transfer apparatus A (2002a) to the transfer apparatus D (2002d), the same channel not used among the four NE from the transfer apparatus A (2002a) to the transfer apparatus B (2002b) may be merely investigated. However, when a total NE number of transfer apparatus is larger than the four NE, the cumbersome investigation of the cross connect setting state is required.
Concretely speaking, in such a case that a ring network is constituted by 10 sets of transfer apparatus with respect to a transfer apparatus having a capacity of 48 channels in a single side, the cross connect setting operations are required 96(=48xc3x972) times by simply calculating a total cross connect setting operation as to a single NE. In the case of such a network constitution, the cross connect setting operations are required (96xc3x9710) times. In another ring network arranged by N sets of NE, the cross connect setting operations are required (96xc3x97N) times. Furthermore, when ADD/DROP is considered, the cross connect setting operations must be executed (96xc3x97Nxc3x972) times.
As apparent from the foregoing descriptions, the larger the scale of this ring network is, the more the times of the cross connect setting operations are increased. When the times of the cross connect setting operations are increased, the probability that an erroneous setting operation happens to occur is necessarily increased. As a consequence, in order to set all lines within a large scale ring network without any erroneous setting operation, line setting workers should carry out very sensitive works for a very long period of time.
The present invention has been made the solve the above-described problems, and therefore, has an object to provide a cross connect apparatus capable of reducing a total work stage required when a setting worker performs a cross connect setting operation, so that a workload imposed on this setting worker is reduced, and thus the cross connect setting operation can be effectively performed.
A first means of the present invention is featured by that in a network through which a synchronized frame signal is multiplexed and the multiplexed frame signal is transferred, the cross connect apparatus is provided at a node connected to the network so as to control one of adding, dropping, and passing-through operations of the frame signal, comprising: control means for analyzing cross connect information contained in the frame signal with which a header is provided to thereby control setting of an own NE, the header containing the cross connect information for indicating whether a signal received from a predetermined node is dropped, or passes through.
As described above, in the transmission source NE, the information for the cross connect setting operation is produced. This information is stored into the header (overhead) of the frame signal (channel), and is notified via the ring network to such a terminal NE to be set via the repeater NE. As a result, it is possible to perform the cross connect setting operation even for a remote NE. Also, in a repeater NE for repeating this cross connect information, the content of this cross connect information is analyzed, so that, for instance, the own NE can execute the setting operation such as pass-through setting operation. As explained above, since the cross connect information successively passes through by using the frame signal (channel), the cross connect setting operations can be realized without any contradictory in and the terminal station, which have function adding, dropping and passing the transfer signal.
A second means is featured by that the control means includes cross connect information editing means for editing the cross connect information based upon an analysis result of the cross connect information.
For example, a transmission source NE, a terminal NE, and a command are registered into the cross connect information, so that since this registered information is analyzed by the terminal NE, the optimum setting operation to the own NE can be done.
A third means is featured by that when the control means recognizes that the own NE is a terminal NE, the control means performs a cross connect setting operation of the own NE based on the cross connect information; produces cross connect response information through the cross connect information editing unit; and returns the cross connect response information to a transmission source NE side.
The terminal NE terminates the cross connect in the own NE based upon the cross connect information produced in the transmission source NE so as to execute this setting operation, and also transmits to the transmission source NE, cross connect response information for indicating that the setting operation is carried out without any problem. Since this cross connect response information is finally received via the repeater NE to the transmission source NE, this transmission source NE can recognize that the cross connect can be set under normal condition.
A fourth means is featured by that in the above-described second means, when the cross connect setting operation of the own NE based on the content of the received cross connect information is not possible, the control means returns cross connect setting abnormal information corrected by the cross connect information editing means to a direction of a transmission source NE.
In such a case that the cross connect setting operation designated by the cross connect setting information cannot be performed in the repeater NE, or the terminal NE, for instance, when a failure happens to occur in a line, or a designated channel is already asigned for another connection, this relevant NE returns the cross connect setting abnormal information to the transmission source NE. As a consequence, the transmission source NE can recognize that the cross connect setting operation cannot be realized.
A fifth means is featured by that in the above-described fourth means, upon receipt of the cross connect setting abnormal information, the control means removes the cross connect setting operation executed when cross connect information corresponding to the cross connect setting abnormal information is received.
Since this cross connect abnormal information is returned, the repeater NE and the like can remove the cross connect setting operation. Accordingly, the useless cross connect setting operation can be avoided.
A sixth means is featured by that in the above-explained first means, the control means includes timer means; commences a measurement by the timer means when the cross connect setting information is received; and returns the cross connect setting abnormal information to a direction of a transmission source NE when the cross connect response information is not received within preset time.
Since the timer is employed, when the cross connect response information cannot be received within the preset time, the repeater NE can separately produce the cross connect setting abnormal information. As a consequence, the cross connects previously set to the NE located prior to the failure NE can be sequentially removed.
A seventh means is featured by that in the above-described sixth means, when the cross connect response information is not received within the time preset by the timer means, the control means returns the cross connect setting abnormal information to the transmission source NE side, and returns cross connect remove information to a reception NE side.
As a consequence, the cross connect setting abnormal condition is notified to the transmission source side, and also the cross connect setting operation previously set in the terminal side. For instance, even when only a single-sided channel of bidirection channels is brought into a failure condition, the cross connect setting operations of both channels can be correctly removed.